Milt,
Sabine schmitz would certainly be the most effective performance upgrade. But I guess she is not always available.
I never experienced a 3.7 Roadster. She should be sufficient power wise. I have a 2010 3.0 Roadster Sport. The power is nice and before I would upgrade the power I enhanced the drivability. Do you have installed upgrades with regards to this topic? I would do that first. Do you have added brake reaction bars? My Roadster has added those plus a second anti tramp bar and a panhard rod. I found that the smooth ride was gone somehow and my wife got a back pain. So I removed the panhard rod. Now it is excellent. A panhard rod comes with disatvantages and now again I habe more feel what the rear is doing despite the lateral movement of the axle. The suspension is very smooth now. But the other alternations which I keep are very valuable. The brake reaction bars make the front stiffer which enhances the overall handling. The second anti tramp bar is a must to let her cope the performance of a 3.7 engine. There was a video last year published on TM where a German guy showed the movement of the cardan without a second anti tramp bar. Shocking up and down movements... Regarding the lateral rear axle movement I will try teflon parts between the frame and the rear springs to avoid this movements as an alternative to the panhard rod.
After all this explanations my qoustion is if your chassis is up to date with the power the 3.7 delivers? As you are located in Cologne PM me and you can try my 3.0 Roadster before you are only focused on performance tuning.
My goal would be to make the engine lighter, not stronger in first place.
